Blister packaging, has applications in a variety of industries including the food and medical markets. But it is in the pharmaceutical area where metered provision to patients of ampoules, tablets or capsules to patients provided in blister packs occurs that it has found its broadest application in the past. This type of packaging typically consists of a thermoformed blister to the top side of which an information bearing material is applied and to the bottom side of which a tear susceptible material such as aluminum foil is applied. Blister packages used in the pharmaceutical industry also have particularly demanding requisites which the packaging industry has found difficult to meet concurrently in a single product formulation.
One of these demands is for a package having high moisture vapor barrier characteristics. This type of barrier is called for to protect stored products from environmentally-based deterioration. Such a barrier can be achieved by including a layer comprised of a fluoro-polymer material such as ACLAR®-laminated vinyl. ACLAR® is a poly chloro-tri-fluoro ethylene film and is a registered trademark of Honeywell, Inc. However, due precisely to their high fluorine content, it is extremely difficult for other substrates to adhere to such films. As a result, it has been necessary to use separate adhesives and adhesive application and curing techniques to achieve a bond between other substrates, such as aluminum foil or PVC, and laminates having a high fluorine content. For example, a dry-bond laminating adhesive may be used to provide adequate adhesion between PVC and a high fluorine content laminate.
In some blister package designs, it is desirable to apply a printed PVC card displaying important product information to one side of a high fluorine content surface and an aluminum foil lidding to its other side. There do not appear to be any adequate aluminum foil or plastics heat seal coatings for sealing to a high fluorine content surface. Consequently, in the past it has been necessary in such cases to produce a basic PVC/Aclar® product using a dry bonding laminating adhesive and then to heat seal aluminum foil to the PVC surface while adhering the printed PVC card to the high fluorine content surface by means of ultrasonic welding. The PVC card is provided with a heat seal coating on the side opposite of the printing to allow for adhering the card to the high fluorine content surface by means of ultrasonic welding. The ultrasonic welding process increases the temperature of the high fluorine content surface and the PVC card, allowing the two materials to fuse together. The resultant product has several disadvantages. First, there is poor adhesion between the high fluorine content surface and the coated surface of the printed PVC card so that the printed PVC cards will occasionally detach from the blister package. The poor adhesion is due to the basic incompatibility between the high fluorine content surface and the adhesive-coated PVC card. Second, the ultrasonic welding increases the temperature of the blister package which can create holes in the package. These holes can compromise the package barrier thereby causing leaking. Finally, the ultrasonic welding of the package is performed manually at a significant cost in time and labor thereby reducing productivity and increasing costs.
There exists, therefore, a need for a material having the high moisture vapor barrier properties of a high fluorine content layer but without the adhesive difficulties inherent in layers comprised of fluoro-polymers alone or the disadvantages encountered when ultrasonic welding is used.